1. Field of the Invention
The present invention relates generally to a supplementary service method for a portable terminal, and in particular, to a method for receiving and processing broadcasting signals.
2. Description of the Related Art
In general, current portable terminals show a tendency to mount a dedicated multimedia processor or strengthen a multimedia function. Research regarding technologies for mounting a television function, and a digital broadcasting receiver function to the portable terminals is ongoing.
In this manner, the portable terminals equipped with the television function, and the digital broadcasting receiver function will make it possible to process data received from each equipment, synchronize audio data and video data, and output the synchronized data.
Currently, standards for digital broadcasting are intensively established all over the world. Digital broadcasting is largely divided into a Digital Multimedia Broadcasting (DMB) scheme in the USA and a Digital Video Broadcasting (DVB) scheme in Europe. The portable terminals having the digital broadcasting receiver function include a tuner, a demodulator, and a decoder, respectively in order to receive the digital broadcasting. Here, the tuner, the demodulator, and the decoder for receiving the digital broadcasting make use of a frequency different from a communication frequency in the portable terminal, as well as demodulating and decoding techniques different from those of the portable terminal.
As for operation of outputting digital broadcasting data in a conventional portable terminal having the digital broadcasting receiver function, when a digital broadcasting channel is first selected, the Radio Frequency (RF) tuner down-converts the frequency of a broadcasting signal of the selected channel to produce an intermediate frequency (IF) signal. The demodulator demodulates a modulated digital broadcasting signal into an original signal. The decoder separates the broadcasting signal demodulated by the demodulator into audio and video signals, as well as decodes and outputs the separated audio and video signals.
As for a more detailed description of the processing operation of the decoder, the decoder receives a Transport Stream (TS) packet from the digital broadcasting signal, demultiplexes the TS packet, and separates the demultiplexed TS packet into audio and video data. The audio data together with the video data are charged in an audio buffer and a video buffer, respectively. At this time, because no data is first charged in the buffers, the buffers are on standby until the data is charged up to a set threshold or more in the buffers. Thereafter, when the data is charged up to the set threshold or more in the buffers, the data is output.
In the conventional portable terminal, a predetermined time is required until the data is charged up to the set threshold or more in the buffers. This time functions as a delay time that it takes to first output the audio and video data after a user selects a specific channel. Further, when the threshold is great, an initial regeneration time of the audio and video data becomes long. In contrast, when the threshold is small, the initial regeneration time becomes short, but a capacity of the data charged in the buffers is not sufficient. In other words, an underflow takes place, thereby causing a sleep state to be entered.